Compact high power alternator

ABSTRACT

A compact, high power, power conversion apparatus including a rotor and a stator. The rotor includes a cylindrical casing, and a predetermined number of permanent magnets disposed on the casing, and is adapted for rotation about the axis of the casing. The stator includes a core and a plurality of sets of conductive windings, each set including a predetermined number of individual conductive windings and associated with an electrical phase. A respective collecting conductor is associated with each set of conductive windings, with each individual conductive winding of the set being electrically connected to the associated collecting conductor. The respective collecting conductors are disposed in a coolant flow path a coolant flow path directing coolant into contact with the stator windings, electrically isolated from each other and spaced apart from each other and from the windings. Collecting conductors in the form of continuous rings and in the form of a plurality of arcs are disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to and fullbenefit of U.S. utility application Ser. No. 11/710,239 filed on Feb.22, 2007, which claims priority to U.S. provisional application No.60/775,904, filed Feb. 22, 2006, and claims priority to and is acontinuation of U.S. patent application Ser. No. 11/347,777, filed Feb.2, 2006, which claims priority to U.S. provisional application No.60/649,720, all of which are incorporated herein by reference in theirentirety for all purposes.

DESCRIPTION OF THE INVENTION

The present invention relates to voltage and current control systems formachines for converting between mechanical and electrical energy, suchas brushless AC generators, and in particular to a control system for acompact permanent magnet high power alternator, such as a compactpermanent magnet high power alternator suitable for automotive use.

BACKGROUND OF THE INVENTION

An alternator typically comprises a rotor mounted on a rotating shaftand disposed concentrically relative to a stationary stator. The rotoris typically disposed within the stator. However, the stator may bealternatively positioned concentrically within the rotor. An externalenergy source, such as a motor or turbine, commonly drives the rotatingelement, directly or through an intermediate system such as a pulleybelt. Both the stator and the rotor have a series of poles. Either therotor or the stator generates a magnetic field, which interacts withwindings on the poles of the other structure. As the magnetic fieldintercepts the windings, an electric field is generated, which isprovided to a suitable load. The induced electric field (which iscommonly known as a voltage source) is typically applied to a rectifier,sometimes regulated, and provided as a DC output power source. Theinduced current is typically applied to a rectifier, sometimesregulated, and provided as a DC output power source. In some instances,a regulated DC output signal is applied to a DC to AC inverter toprovide an AC output.

Conventionally, alternators employed in motor vehicle applicationstypically comprise: a housing, mounted on the exterior of an engine; astator having 3-phase windings housed in the housing, a belt-drivenclaw-pole type (e.g. Lundell) rotor rotatably supported in the housingwithin the stator. However, to increase power output the size of theconventional alternator must be significantly increased. Accordingly,space constraints in vehicles tend to make such alternators difficult touse in high output, e.g. 5 KW, applications, such as for powering airconditioning, refrigeration, or communications apparatus.

In addition, the claw-pole type rotors, carrying windings, arerelatively heavy (often comprising as much as three quarters of thetotal weight of the alternator) and create substantial inertia. Suchinertia, in effect, presents a load on the engine each time the engineis accelerated. This tends to decrease the efficiency of the engine,causing additional fuel consumption. In addition, such inertia can beproblematical in applications such as electrical or hybrid vehicles.Hybrid vehicles utilize a gasoline engine to propel the vehicle atspeeds above a predetermined threshold, e.g. 30 Kph (typicallycorresponding to a range of RPM where the gasoline engine is mostefficient). Similarly, in a so-called “mild hybrid,” a starter-generatoris employed to provide an initial burst of propulsion when the driverdepresses the accelerator pedal, facilitating shutting off the vehicleengine when the vehicle is stopped in traffic to save fuel and cut downon emissions. Such mild hybrid systems typically contemplate use of ahigh-voltage (e.g. 42 volts) electrical system. The alternator in suchsystems must be capable of recharging the battery to sufficient levelsto drive the starter-generator to provide the initial burst ofpropulsion between successive stops, particularly in stop and gotraffic. Thus, a relatively high power, low inertia alternator isneeded.

In general, there is in need for additional electrical power forpowering control and drive systems, air conditioning and appliances invehicles. This is particularly true of vehicles for recreational,industrial transport applications such as refrigeration, constructionapplications, and military applications.

For example, there is a trend in the motor vehicle industry to employintelligent electrical, rather than mechanical or hydraulic control anddrive systems to decrease the power load on the vehicle engine andincreased fuel economy. Such systems may be employed, for example, inconnection with steering servos (which typically are active only asteering correction is required), shock absorbers (using feedback toadjust the stiffness of the shock absorbers to road and speedconditions), and air conditioning (operating the compressor at theminimum speed required to maintain constant temperature). The use ofsuch electrical control and drive systems tends to increase the demandon the electrical power system of the vehicle.

Similarly, it is desirable that mobile refrigeration systems beelectrically driven. For example, driving the refrigeration system atvariable speeds (independently of the vehicle engine rpm) can increaseefficiency. In addition, with electrically driven systems the hosesconnecting the various components, e.g. the compressor (on the engine),condenser (disposed to be exposed to air), and evaporation unit (locatedin the cold compartment), can be replaced by an electrically drivenhermetically sealed system analogous to a home refrigerator orair-conditioner. Accordingly, it is desirable that a vehicle electricalpower system in such application be capable of providing the requisitepower levels for an electrically driven unit.

There is also a particular need for a “remove and replace” high poweralternator to retrofit existing vehicles. Typically only a limitedamount of space is provided within the engine compartment of the vehicleto accommodate the alternator. Unless a replacement alternator fitswithin that available space, installation is, if possible, significantlycomplicated, typically requiring removal of major components such asradiators, bumpers, etc. and installation of extra brackets, belts andhardware. Accordingly, it is desirable that a replacement alternator fitwithin the original space provided, and interfaces with the originalhardware.

In general, permanent magnet alternators are well known. Suchalternators use permanent magnets to generate the requisite magneticfield. Permanent magnet generators tend to be much lighter and smallerthan traditional wound field generators. Examples of permanent magnetalternators are described in U.S. Pat. Nos. 5,625,276 issued to Scott etal on Apr. 29, 1997; 5,705,917 issued to Scott et al on Jan. 6, 1998;5,886,504 issued to Scott et al on Mar. 23, 1999; 5,929,611 issued toScott et al on Jul. 27, 1999; 6,034,511 issued to Scott et al on Mar. 7,2000; and 6,441,522 issued to Scott on Aug. 27, 2002.

Particularly light and compact permanent magnet alternators can beimplemented by employing an “external” permanent magnet rotor and an“internal” stator. The rotor comprises a hollow cylindrical casing withhigh-energy permanent magnets disposed on the interior surface of thecylinder. The stator is disposed concentrically within the rotor casing,and suitably comprises a soft magnetic core, and conductive windings.The core is generally cylindrical width an axially crenellated outerperipheral surface with a predetermined number of equally spaced teethand slots. The conductive windings (formed of a suitably insulatedelectrical conductor, such as varnished copper motor wire), are woundthrough a respective slot, outwardly along the side face of the corearound a predetermined number of teeth, then back through another slot.The portion of the windings extending outside of the crenellation slotsalong the side faces of the core are referred to herein as end turns.Rotation of the rotor about the stator causes magnetic flux from therotor magnets to interact with and induce current in the statorwindings. An example of such an alternator is described in, for example,the aforementioned U.S. Pat. Nos. 5,705,917 issued to Scott et al onJan. 6, 1998 and 5,92,611 issued to Scott et al on Jul. 27, 1999.

The power supplied by a permanent magnet generator varies significantlyaccording to the speed of the rotor. In many applications, changes inthe rotor speed are common due to, for example, engine speed variationsin an automobile, or changes in load characteristics. Accordingly, anelectronic control system is typically employed. An example of apermanent magnet alternator and control system therefore is described inthe aforementioned U.S. Pat. No. 5,625,276 issued to Scott et al on Apr.29, 1997. Examples of other control systems are described in U.S. Pat.No. 6,018,200 issued to Anderson, et al. on Jan. 25, 2000. Otherexamples of control systems are described in commonly owned co-pendingU.S. patent application Ser. No. 10/860,393 by Quazi et al, entitled“Controller for Permanent Magnet Alternator” and filed on Jun. 6, 2004and No. 11/347,777 by Faber man et al (including the present inventors),entitled “Controller for AC Generator” and filed Feb. 2, 2006. Theaforementioned commonly owned applications are hereby incorporated byreference as if set forth verbatim herein.

The need to accommodate a wide range of rotor speeds is particularlyacute in motor vehicle applications. For example, large diesel truckengines typically operate from 600 RPM at idle, to 2600 RPM at highwayspeeds, with occasional bursts to 3000 RPM, when the engine is used toretard the speed of the truck. Thus the alternator system is subject toa 5:1 variation in RPM. Light duty diesels operate over a somewhat widerrange, e.g. from 600 to 4,000 RPM. Alternators used with gasolinevehicle engines typically must accommodate a still wider range of RPM,e.g. from 600 to 6500 RPM. In addition, the alternator must accommodatevariations in load, i.e., no load to full load. Thus the output voltageof a permanent magnet alternator used with gasoline vehicle engines canbe subject to a 12:1 variation. Accordingly, if a conventional permanentmagnet alternator is required to provide operating voltage (e.g. 12volts) while at idle with a given load, it will provide multiples of theoperating voltage, e.g. ten (10) times that voltage, at full engine RPMwith that load, e.g. 120 volts. Where the voltage at idle is 120 V, e.g.for electric drive air conditioning, or communications apparatus, thevoltage at full engine RPM would be, e.g. 1200 volts. Such voltagelevels are difficult and, indeed, dangerous to handle. In addition, suchextreme variations in the voltage and current may require more expensivecomponents; components rated for the high voltages and currents producedat high engine RPM (e.g. highway speeds) are considerably moreexpensive, than components rated for more moderate voltages.

The stator of a conventional high current motor vehicle alternator isconstructed with conductors of large cross sectional area effectivelyconnected in series. More particularly, coil groups, one associated witheach phase (the A, B and C Phase) are conventionally employed. Therespective Phase coil groups, (A, B and C) are connected together(terminated) as a ‘WYE’ or ‘Delta’ at one end. The opposite ends of thecoil groups are arranged by phase so that each phase is isolated andthen terminated to both collect and exit the alternator to a voltagecontrol. On the exiting termination end, the coil ends of like phasesare soldered in groups to insulated motor lead wire. These motor leadwires may then in turn be soldered in groups to even larger gauge motorlead wire culminating in three separate conductors for each phase, A, Band C. The lead wires are then secured to the stator by lashing theconductors to the end turns of the stator. Lashing conductors to endturns reduces the amount of exposed copper to cooling fluid passingthrough the alternator, in effect acting as an insulating blanket andhindering cooling of the end turns and lead wires. Several additionalproblems can exist with this winding method. For example: because of thelow number of turns (in some instances only a single turn) per polephase coil, it is difficult or impossible to make a small change indesign output voltage by changing the number of turns of the phase polecoil; the large cross sectional area of the conductors make the statordifficult to wind; and a short circuit between coils will typically burnout the entire stator and may stall the alternator, resulting inpossible damage to the drive system or overloading the vehicle engine.

In general, permanent magnet alternators incorporating a predeterminednumber of independent groups of windings, wound through slots aboutpredetermined numbers of teeth where the power provided by each group isrelatively unaffected by the status of the other groups are known. Forexample, such an alternator is described, together with a controllertherefor, in U.S. Pat. No. 5,900,722 issued to Scott et al. on May 4,1999. In the alternator described in U.S. Pat. No. 5,900,722, the numberof groups of windings was equal to an integer fraction of the number ofpoles, and the controller circuit selectively completed current paths tothe individual groups of windings to achieve a desired output.

However, there remains a need for a compact high power alternatorwherein a desired output voltage can be achieved by changing the numberof turns of the phase pole coil, that is relatively easy to wind, andminimizes the consequence of short circuits, while at the same timefacilitating cooling.

SUMMARY OF THE INVENTION

In accordance with various aspects of the present invention, the statorwinding is wound with a predetermined number of pole phase coils,preferably equal to the number of magnetic poles. Each pole phase coilis wound with enough turns to generate the required output voltage ofthe alternator and a fraction of the output current equal to 1 dividedby the number of magnetic poles. These individual pole phase coils arethen connected in parallel.

In accordance with another aspect of the present invention, a respectiveconducting phase ring corresponding to each output phase is installedwithin the alternator with each coil corresponding to the associatedphase electrically connected to the conducting phase rings to facilitatecooling and grouping and transmission of output phases to the control

In accordance with another aspect of the present invention theconducting phase rings are held in place by a non-conducting supportstructure.

In accordance with another aspect of the present invention theconducting phase rings are disposed to provide an efficient cooling byexposure to the cooling fluids e.g. air, passing over the conductingphase rings and end turns.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will hereinafter be described in conjunction withthe figures of the appended drawing, wherein like designations denotelike elements (unless otherwise specified).

FIG. 1 is a block schematic of a system for converting betweenmechanical and electrical energy.

FIG. 2A is a side view of the exterior of an alternator in accordancewith various aspects of the present invention.

FIG. 2B is a sectional view along A-A of the alternator of FIG. 2A.

FIG. 2C is a simplified sectional view along B-B of the alternator ofFIG. 2A showing the relative placement of the conducting phase ringswithin the alternator.

FIG. 2D is simplified sectional view of a terminal in the alternator ofFIG. 2A.

FIG. 2E is a diagram showing an alternative embodiment of a conductingphase ring.

FIG. 2F is a simplified perspective view of the stator core, and theconducting phase rings of the alternator of FIG. 2A, illustrating theconnections between the conducting phase rings and respective groups ofwindings (winding end turns omitted).

FIG. 2G is a block schematic wiring diagram of an alternator utilizingphase rings in accordance with the present invention adapted to producea DC voltage output.

(FIGS. 2A-2G are collectively referred to as FIG. 2).

FIG. 3A is a side view of the exterior of an alternative embodimentalternator in accordance with various aspects of the present invention.

FIG. 3B is a sectional view along C-C of the alternator of FIG. 3A.

FIG. 3C is a simplified perspective view of the stator core, and thesegmented conducting phase rings of the alternator of FIG. 3A,illustrating the connections between the segmented conducting phaserings and respective groups of windings (winding end turns omitted).

FIG. 3D is a block schematic wiring diagram of an alternator utilizingsegmented conducting phase rings in accordance with the presentinvention adapted to produce a D.C. voltage output. (FIGS. 3A-3D arecollectively referred to as FIG. 3).

FIG. 4A is a top view of the exterior of an alternative embodimentalternator in accordance with various aspects of the present invention.

FIG. 4B is a sectional view along D-D of the alternator of FIG. 4A.

FIG. 4C is a simplified perspective view of the stator core, and themulti-segmented conducting phase rings of the alternator of FIG. 3A,illustrating the connections between multi-segmented conducting phaserings and respective groups of windings (winding end turns omitted).

FIG. 4D is a block schematic wiring diagram of an alternator utilizingmulti-segmented conducting phase rings in accordance with the presentinvention adapted to produce a D.C. voltage output. (FIGS. 4A-4D arecollectively referred to as FIG. 4).

FIG. 5 is a schematic wiring diagram illustrating three individualwindings of a three phase pole group of the stator used in each of theembodiments of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, a power conversion apparatus, such as analternator 102, in accordance with various aspects of the presentinvention, suitably cooperates with a rectifying control system 100 anda source of mechanical energy (e.g. drive) 104, e.g. an engine orturbine, a load 106, such as a motor and, if desired, in energy storagedevice 108, such as a battery, capacitor, or flywheel.

Rectifying control system may be any system suitable for rectifying theAC signal from alternator 102, i.e. converting it into a DC signal, andregulating the voltage of that signal at a predetermined level, e.g.28V. In the preferred embodiment, system 100 comprises a controller 110and a switching bridge112 such as described in commonly owned U.S.patent application Ser. No. 11/347,777 by Faber man et al (including thepresent inventors), entitled “Controller for AC Generator” and filedFeb. 2, 2006. If desired, an inverter (sometimes categorized ascomprising part of load 106) can also be provided to generate an ACsignal at a constant predetermined frequency and amplitude (e.g. 60 Hz,120V).

In general, alternator 102 generates AC power in response to mechanicalinput from energy source 104. Alternator 102 preferably providesmulti-phase (e.g. three-phase, six-phase, etc.) AC output signals, e.g.phase A (118), phase B (120), and phase C (122). Those output signalsare typically unregulated and may vary significantly in accordance withdrive RPM (source 104).

The AC phase signals from alternator 102 are applied to system 100,preferably through input fuses 128. System 100 rectifies the AC signalfrom alternator 102, i.e. converts it into a DC signal and regulates thevoltage of that signal at a predetermined level, e.g. 28V. In thepreferred embodiment, switching bridge 112 selectively, in response tocontrol signals from controller 110, provides conduction paths betweenthe various phases of the AC signal from alternator 102 and a load 106.Exemplary switching bridges 112 are shown in commonly owned co-pendingU.S. patent application Ser. No. 11/347,777 by Faber man et al(including the present inventors), filed Feb. 2, 2006. Controller 110selectively generates control signals to switching bridge 112 to producea regulated output signal at a predetermined voltage. Controller 110suitably samples the regulated output either locally at input 114, orremotely at input 140 and adjusts the signals to bridge 112 to maintainthe proper output. Additionally, the output current is sensed at input116 to further modify the control signals to bridge 112.

The regulated DC signal Voltage Regulated Output (VRO) is then applied,suitably through an output fuse 136, to load 106 and energy storagedevice 108. Load 106 may be any device that uses power, such as, e.g.lights, motors, heaters, electrical equipment, power converters, e.g.inverters or DC-to-DC converters. Energy storage device 108 filters orsmoothes the output of control system 110 (although, in variousembodiments, controller 110 may itself incorporate or otherwise provideadequate filtering).

If desired, other outputs, 150, and 160, may be provided by system 100.In addition, a suitable crowbar circuit 142 may be provided for systemprotection.

Alternator 102 is preferably an alternator generally of the typedescribed in commonly owned co-pending U.S. patent application Ser. No.10/889,980 by Charles Y. Lafontaine and Harold C. Scott, entitled“Compact High Power Alternator” and filed on Jul. 12, 2004, but includesfor each pole, a respective group of windings (including at least onewinding corresponding to each phase) with all of the windingscorresponding to a given phase connected in parallel. The aforementionedLafontaine et al application is hereby incorporated by reference as ifset forth verbatim herein.

In accordance with one aspect of the present invention, a parallelconnection between coils corresponding to the same phase is effectedthrough a corresponding conducting phase ring 138, and includes fusiblelinks 124, disposed between the conducting phase rings 138, and theoutput terminals 262 of the alternator. The output of each individualcoil is collected by its respective conducting phase ring 138, which isin turn attached to its respective output terminal126.

As the total number of poles in alternator 102 increases, so too do thenumber of individual coils. The conventional method of gathering coilsinvolves soldering the motor wire to conventionally insulated motor leadwire. As the rated output of the alternator increases, a correspondingincrease in the load carrying capacity of the motor lead wire is alsorequired. Increasing load demand on the lead motor wire is typically metby increasing the cumulative gauge of the wire, either by increasing thegauge of a single wire or by using multiple wires in parallel. The neteffect is increasingly large cross sectional areas of motor lead wire.When considering the total number of coils and their respective endturns along with the lead wire and its associated insulation, theresulting stator assembly with conductor and motor lead wire tiedtogether insulate the end turns, detrimental to cooling. The resultingassembly also restricts the only available coolant flow (e.g., airflow)over the end turns further reducing cooling.

Thus, there is a need for a compact high power alternator wherein adesired output voltage can be achieved by changing the number of turnsof the phase pole coil, that is relatively easy to wind, and minimizesthe consequence of short circuits, while at the same time facilitatingcooling. In accordance with various aspects of the present inventionthis is achieved by employing a predetermined number of pole phasecoils, preferably equal to the number of magnetic poles, with pole phasecoil wound with enough turns (of a relatively small diameter wire) togenerate the required output voltage of the alternator and a fraction ofthe output current equal to 1 divided by the number of magnetic polesand connecting the individual pole phase coils in parallel, preferablyemploying conducting phase rings (collectors) 138. Use of conductingphase rings 138 not only greatly simplifies assembly of alternator 102,but also facilitates cooling of the windings.

More particularly, alternator 102 preferably comprises: a shaft 202,preferably including a tapered projecting portion 204 and a threadedportion 206; a rotor 208; a stator 210; a front endplate 212; a frontbearing 214; a jam nut 216; a rear endplate 218; a rear shaft retainingring 220; a rear bearing 222; a rear jam nut 224; an outer casing 226and respective tie rods (not shown). Rotor 208 is mounted on shaft 202for rotation with the shaft. Stator 210 is closely received within rotor208, separated from rotor 208 by a small air gap 228. Front endplate212, front bearing 214, rear bearing 222, rear endplate 218, outercasing 226 and tie rods cooperate as a support assembly to maintainalignment of shaft 202, rotor 208, and stator 210. Shaft 202 ismaintained by bearings 214 and 222, which are mounted on front endplate212 and rear endplate 218, respectively, and rotatably maintain andalign shaft 202 concentric and perpendicular with the endplates. Rotor208 is mounted for rotation on shaft 202, positively positioned bycooperation with tapered shaft portion 204. Rear endplate 218 mounts andlocates stator 210 so that it is disposed within rotor 208 properlyaligned with shaft 202 and rotor 112. Outer casing 226 has end facesperpendicular to its axis (is preferably cylindrical) and is disposedbetween front endplate 212 and rear endplate 218. Tie rods compressendplates 218 and 212 against outer casing 226, keeping the componentssquared and in alignment.

In a typical automotive alternator application, a pulley 230 is mountedon the end of shaft 202. Power from an engine (e.g., 104, not shown inFIG. 2) is transmitted through an appropriate belt drive (not shown) topulley 230, and hence shaft 202. Shaft 202 in turn causes rotor 208 torotate about stator 210. Rotor 208 generates a magnetic field, whichinteracts with the windings on stator 210. As the magnetic fieldintercepts the windings, an electrical current is generated, which isprovided to a suitable load.

Rotor 208 preferably comprises an endcap 232, a cylindrical casing 234and a predetermined number (e.g. 16 pairs) of alternatively poledpermanent magnets 236 disposed in the interior side wall of casing 234.Rotor endcap 232 is suitably substantially open, including a peripheralportion 238, respective cross-arms (not shown) and a central hub 240 toprovide for connection to shaft 202. Respective coolant (e.g., air)passageways 242 are provided through endcap 234, bounded by peripheralportion 238 adjacent cross arms (not shown), and central hub 240.

Stator 210 suitably comprises a core 244 and conductive windings (shownschematically) 280. Core 244 suitably comprises laminated stack of thinsheets of soft magnetic material, e.g. non-oriented, low loss (leadfree) steel, that are cut or punched to the desired shape, aligned andjoined. Core 244 is generally cylindrical, with an axially crenellatedouter peripheral surface, i.e., includes a predetermined number of teethand slots. Core 244 is preferably substantially open, with a centralaperture, and suitably includes crossarms with axial through-bores tofacilitate mounting to rear endplate 218.

Front endplate 212 is suitably generally cylindrical, including: acentrally disposed hub 246, including a coaxial aperture that locatesfront bearing 214; a peripheral portion and including respective tappedholes (not shown) disposed at predetermined radial distances from thecentral aperture, distributed at equal angular distances, to receive tierods (not shown); and respective (e.g., 4) crossarms (not shown)connecting peripheral portion 248 to hub 246, and defining respectivecoolant (e.g., air) passages 250

Rear endplate 218 carries and locates rear bearing 222, and mounts andlocates stator core 244. Rear endplate 218 suitably includes a steppedcentral hub 252 having a forward reduced diameter portion 254 andcentral aperture 256 there through, and is generally cylindricalpreferably having the same outer diameter as front endplate 212,connected to hub 252 by respective crossarms (not shown). Rear endplate218 also suitably includes respective coolant (e.g., air) passageways258, bounded by adjacent crossarms (not shown), outer portion 260, andhub 252.

The output from stator windings 280 is collected by phase rings 138 andprovided at respective output terminals 262. More particularly, outputterminals 262 (one for each phase) are suitably provided in rearendplate 218. Terminals 262 are suitably electrically connected throughfusible links 124, to associated conducting phase rings (collectors)138. Output terminals 262 and fusible links 124 are positioned radiallyabout conducting phase rings 138. The respective phase rings 138collect, e.g. are electrically connected to, through, e.g., conductors276, each of the individual coils with the associated phase. Respectiveindividual conducting cables (e.g. 294 in FIG. 2G) are attached toterminals 262 to transmit phase output to the control 100.

Conducting phase rings 138 are made of a suitable conductive materiale.g. plated copper. Phase rings 138 are suitably uninsulated orminimally insulated (e.g. with varnish) to facilitate cooling andsufficiently stiff or rigid to facilitate isolation from each other oncemounted and subjected to environmental forces/acceleration. Theconducting phase rings may be formed of rod stock or punched from asheet of appropriate material. In the embodiment of FIG. 2, conductingphase rings 138 are each continuous e.g. a single piece rod stock withit ends connected by e.g., soldering or brazing, to form a continuousconducting ring.

Use of solid continuous phase rings 138 are particularly advantageous inthat dual current paths to fusible link 124 permits use of lower gauge(and thus lighter and less expensive) material for phase rings 138. Whena solid, a continuous phase ring 138 is utilized, the current iseffectively split at a point 180 degrees opposite the point at whichfusible link 124 is attached. All current produced by conductors 276 onone half of the phase ring exit to fusible link 124 effectively remainson that half, current produced on the opposite half follows that path tofusible link 124. The result is a phase ring approximately half thegauge of a conductor with only a single path to fusible link 124.

The respective rings 138 are disposed in the coolant flow path,electrically isolated and spaced apart from each other and from rearendplate 218. Conducting phase rings 138 are suitably mechanicallyfastened to endplate 218 using a non-conducting conducting phase ringmounting structure 264 preferably made of a high impact resistant andchemically stable material e.g. polyamide-imide, so that each conductingphase ring, one for each phase output, are physically spaced apart andisolated electrically from each other and rear endplate 218. Conductingphase rings 138 are positioned in coolant (e.g., air) passage 258 tomaximize exposure to coolant (e.g., air) flow produced by alternator102. The exposure to airflow is further maximized by progressivelyvarying the diameter of adjacent phase rings. For example, the phasering 138 associated with phase A (terminal 118) is disposed closest tothe interior of endplate 218, but of a relatively large diameter(suitably approaching the outer diameter of coolant (e.g., air) passage258 in endplate 218). The phase ring 138 associated with phase B(terminal 120) is suitably coaxially disposed but offset rearwardly, andwith a smaller diameter (the outer diameter of the phase B ring suitablyless than the inner diameter of the phase A ring by a predeterminedamount). The phase ring 138 associated with phase C (terminal 122) islikewise suitably coaxially disposed but offset rearwardly from thephase B ring 138, and with a smaller diameter (the outer diameter of thephase C ring suitably less than the inner diameter of the phase B ringby a predetermined amount). This alignment, made possible by phase ringmounting structure 264, presents each ring to cooling air flow at closeto ambient inlet temperature as possible. Preferably, the rings farthestfrom the ambient inlet have the larger diameters.

Referring to FIG. 2D, output terminal assembly 126 suitably comprises athreaded conducting stud 266, preferably a highly conductive corrosionresistant material (e.g. plated copper) along with an electricallynon-conductive bushing 268, preferably a high impact resistant andchemically stable material (e.g. polyamide-imide), to electricallyisolate the output terminal from alternator rear endplate 218. Thethreaded conducting stud 266 in the preferred embodiment has anincorporated shoulder 270, to act as a seat from inside alternator rearendplate 218 to which nut 272 can be tightened, capturing the assemblyin rear endplate 218.

Fusible link 124 is made of a suitable material e.g. a calculateddiameter and length of wire (preferably plated copper) that will meltwhen subjected to loads calculated to be destructive to alternator 102,control 100 or electrical systems being powered by said equipment. Inthe preferred embodiment fusible link 124 is soldered or brazed to boththe threaded conducting stud 266 and conducting phase ring 138. Analternate method to secure the fusible link is to attach a suitable lugto the end of fusible link 124 which is then fastened to stud 266mechanically by means of a threaded nut.

Referring particularly to FIGS. 2B and 2C, conducting phase rings 138are fastened to structure 264. Conducting phase rings 138 are disposedin the coolant path, exposed to coolant flow (e.g., airflow) 274,cooling conducting phase rings 138 as well as conductors 276 (connectingthe coil windings to phase rings 138). Ring mounting structure 264 ispositioned to produce a gap between phase rings 138 and the stator endturns (not shown). This gap exposes the rear stator end turns to coolingfluid that would not be available in a conventionally wound stator.

Coolant (e.g. cooling air) continues through the alternator and impingesupon winding end turns 280 of stator 210 cooling the end turns. Airflowthen divides and proceeds through stator core 244 and into cavity 278 atwhich point it cools the far end turns of stator 210. The other dividedairflow passes between rotor casing 234 and outer casing 226 coolingrotor casing 234 and magnets 236. The divided airflow rejoins in airpassageway 250 and leaves the alternator to centrifugal fan 282.

Conductors 276, comprising an A phase 118, B phase 120 and C phase122component of a single three-phase pole group, as will be describedlater, exit stator 210 and are soldered or brazed to their respectiveassociated conducting phase rings 138. Conductors 276 in the preferredembodiment are exposed to airflow 274. In certain cases it may bedesirable to sheath conductors 276 with a thin walled electricallyisolating material e.g. Nomex to protect against grounding.

Referring now to FIG. 2 E. an alternate method of producing conductingphase ring 138 is accomplished by forming it of rectangular stock suchthat suitable surfaces are presented for drilling and tapping holes 284.The end of fusible link 124 can, in this embodiment, be attached with asuitable lug 286 for fastening by, e.g. a threaded fastener 288 toconducting phase ring 138. Equally, conductor 276 can also be equippedwith a similar lug and fastened to conducting phase ring 138 usingfastener 290. Conducting phase ring 138 is in turn secured in a similarmanner to rear endplate 218 using an appropriate structure similar to264. Alternatively slots 292 may be cut into each phase ring at regularintervals in which individual conductors exiting the stator can besoldered. This method of assembly has a major advantage over previouslydescribed methods of fastening conductors 276 to phase rings 138 in thatautomation of assembly can be implemented by modifying existingultrasonic soldering equipment used to terminated conductors in electricmotor manufacturing.

Referring now to FIG. 2F, stator 210 is shown, for clarity, withoutcoils, and with individual conductors 276 in greatly reduced detail. Inthis particular embodiment, the respective phase rings 138 associatedwith each of the three A, B and C phases are continuous either bysoldering, brazing or machined from a single piece of un-insulated,corrosion resistant conductive material e.g. plated copper. Terminals126, represented graphically, correspond to A phase 118, B phase 120 andC phase 122. The output of each pole group is collected within thealternator through the phase rings 138 and exits the alternator viathree conductors that that representing all three phases to control 100.

Referring now to FIG. 2G. individual conductors 276 from the respectiveA phase, B phase and C phase windings 118, 120, and 122 are terminatedon respective collection phase rings 138 which then in turn are carriedto control 100 via conductors 294. The output from control 100 resultsin a voltage regulated output or VRO, of an application specific voltagee.g. 28 VDC.

Conductors 294, coupled between output terminals 264 and control 100 aresuitably of sufficient gauge to adequately carry the current. As thegauge of a wire or cable increases, it becomes increasingly difficult toroute cables due to the larger bend radius found in large gauge wire. Asa result it is difficult to use very large gauge wire or cable in manyapplications. As will be discussed, in applications in which very largeconductors may not be appropriate it is possible then to segment phaserings into multiple sections in which each phase ring section isassigned an appropriately sized conductor to carry the reduced currentproduced by that specific section.

For example, current requirements may be reduced by employing phaserings split into a plurality of groups. Referring now to FIG. 3A-3D, analternator 302 employing two sets of phase rings 306 with correspondingterminals 126 and fusible links 124, cooperate with associated controls308 and 310. Phase rings 310 are separated electrically at point 312 and314. Each group carries respective A phase, B phase and C phasecomponents each leading to their respective controls 308 and 310. Rearend plate 304 is similar in all respects to end plate 218 in all but onefeature in that it is machined to accept a second set of terminals 126.

Referring now to FIG. 3D, phase ring portions 306 each receive theirrespective conductors 276 from stator 210. Phase ring portions 306 areelectrically connected via terminals 126, conductors 316 to controls 308and 310. When terminal 126 is connected in the middle of phase ringportion 306, the current is effectively split at the point at whichfusible link 124 is attached. All current produced by conductors 276 onone half of the phase ring portion exit to fusible link 124 effectivelyremains on that half, current produced on the opposite half follows thatpath to fusible link 124. The result is a phase ring portionapproximately half the gauge of a conductor with only a single path tofusible link. The gauge of conductors 316 can be sized according toapplication specific requirements. Modern engine compartments have verylittle space to offer when considering, for example, the size ofconductor required to properly conduct 600 amps of power at 28 VDC. Byhalving the current carried by conductors 316 in very high outputapplications, routing of cables becomes much more manageable. There is acorresponding benefit in the controls as well. As amperage increases thesize and cost of components increases, but not in a linear fashion.Therefore by halving the current carried by the conductors and thecontrol components as well, a savings in space and cost is achieved.

Current requirements can be further reduced by splitting the phase ringsinto a plurality of portions. For example, referring to FIGS. 4A-4D, thephase rings can be broken into four sections 406, electrically separatedat points 416, 418, 420, and 422. An associated set of terminals 118,120, 122 is provided for each phase ring segment, connected torespective controls 408, 410, 412, and 414. As with phase ring portions306, terminal 126 is connected in the middle of phase ring portion 406,the current is effectively split at the point at which fusible link 124is attached. All current produced by conductors 276 on one half of thephase ring portion exit to fusible link 124 effectively remains on thathalf, current produced on the opposite half follows that path to fusiblelink 124. The result is a phase ring portion approximately half thegauge of a conductor with only a single path to fusible link. Theoutputs of controls 408, 410, 412, and 414 are connected in parallel toprovide outputs VRO+ and VRO−.

As previously noted, stator core 210 is generally cylindrical with anaxially crenellated outer peripheral surface having a predeterminednumber of equally spaced teeth and slots. The conductive windings(formed of a suitably insulated electrical conductor, such as varnishedcopper motor wire), are wound through a respective slot, outwardly alongthe side face of the core around a predetermined number of teeth, thenback through another slot. Referring now to FIG. 5, stator core 210includes a predetermined number of slots, e.g. 36 (shown schematicallyin FIG. 5, indicated by numerals 1-36). The conductive windings includea predetermined number of individual phase coils (A phase, B phase, andC phase) corresponding to each magnetic pole in the rotor. Individualpole phase coils of a three phase alternator comprise an A pole phasecoil 518, B pole phase coil 520 and C pole phase coil 522 whichcollectively make up a pole phase coil group 526. There is one polephase coil group for each pole of an alternator (e.g. 12 pole phase coilgroups in a 12-pole alternator) cooperating in a “Wye” connection 524.The pole phase coil conductors 526 of a 12 pole alternator are attachedto their respective conducting phase ring 506, 508 and 510.

For example, an individual pole phase coil 522 (C phase of pole group 1)is wound around slots #36 and #3 of stator 210. The number of turns ofconductor 526 comprising coil 522 is equal to the number of turnsrequired to generate the rated output voltage of one phase of thealternator. The output current portion of the individual phase coil isequal to 1 divided by the number of magnetic poles of the alternator.Thus, the individual pole phase coil is made up of a relatively largenumber of turns of relatively small wire.

This construction results in a number of advantages, both duringconstruction of the alternator and during operation of the alternator.

Because each individual pole phase coil is made up of a relatively largenumber of turns, small changes in design voltage can be accomplished bychanging the number of turns. For example, a particular 12 polealternator wound in a conventional manner with all of the pole phasecoils connected in series may require 1.0417 turns of conductor equal towire gage 6.285 to produce 14 VDC (after proper rectification), 300amperes at 1940 rpm. Neither the number of turns nor the equivalent wiregage is practical numbers for production. By constructing the examplealternator with the pole phase coils connected in parallel, eachindividual pole phase coil would be 12.5 turns of 17 gage wire. (As anote, half turns can be constructed by terminating one end of theindividual pole phase coil, say the start, on one side of the statorlamination stack, and the other end, say the finish, at the other sideof the stator lamination stack. This construction is illustrated in FIG.18A) Further to this example, increasing the original design to 1.0833turns (again, an impractical number) would reduce the rpm to 1894. Thiscould be accomplished in the alternate construction by increasing eachparallel pole phase coil to 13 turns. The relatively small crosssectional area of the conductors provides for easier winding of thecoils.

A short circuit between turns of an individual pole phase coil resultsin most of the power being generated in the alternator flowing in theshorted coils. Because the coils are constructed of a relatively largenumber of turns of relatively small cross sectional area conductors, theshorted turns will very quickly melt and clear the short circuit. Thedecrease in output power resulting from one pole phase coil opening upis approximately 1/(number of magnetic poles+number of phases). Forexample the power output reduction of a 12 pole, three-phase alternatorwith one pole phase coil shorted and then self cleared is approximately3%.

For example, a short circuit between turns of an individual pole phasecoil will typically clear in less than two seconds. Damage to thealternator drive system is eliminated, the engine continues operationwith no additional load and the alternator continues to produce power tothe connected load. Conducting phase rings 138 are individuallyidentified as A ring 506, B ring 508 and the C ring 510. Threeindividual pole phase coil conductors, A phase 512, B phase 514 and Cphase516 are schematically illustrated for clarity. Each of the threepole phase coils that make up a pole phase coil group is, in thisillustration connected in a “Wye” connection 524. As noted earlier, theuse of a “Delta” connection can also be implemented using phasecollector rings.

The individual phase coil conductors are gathered in an efficient mannerthat does not impede cooling. With phase coil conductors leaving thephase coil end turn at 90 degrees to the face of stator 210, the endturns are exposed to the greatest air flow possible which in turn offersthe best possible cooling of said end turns.

Although the present invention has been described in conjunction withvarious exemplary embodiments, the invention is not limited to thespecific forms shown, and it is contemplated that other embodiments ofthe present invention may be created without departing from the spiritof the invention. Variations in components, materials, values, structureand other aspects of the design and arrangement may be made inaccordance with the present invention as expressed in the followingclaims.

1. A compact, high power, power conversion apparatus comprising: a rotorcomprising a cylindrical casing, and a predetermined number of permanentmagnets disposed on the casing, the rotor being adapted for rotationabout the axis of the casing; a stator comprising a core and a pluralityof sets of conductive windings, each set including a predeterminednumber of individual conductive windings and associated with anelectrical phase, and each set of individual conductive windingsassociated with an electrical phase is further partitioned into phasesubgroups; a respective set of collecting conductor arcs respectivelyassociated with each phase subgroup, each individual conductive windingof the respective phase subgroup being electrically connected inparallel to the associated collecting conductor arc; and a coolant flowpath directing coolant into contact with the stator windings; therespective collecting conductor arcs being disposed in the coolant flowpath electrically isolated from each other and spaced apart from eachother and from the windings. wherein the collecting conductors eachcomprise, for each electrical phase, a respective set of a predeterminednumber of electrically isolated conductive arcs.
 2. The apparatus ofclaim 1 wherein each of the conductive arcs associated with one phase ofthe electrical phases are equally sized.
 3. The apparatus of claim 1further including an output terminal assembly associated with eachconductive arc, electrically connected to the arc at a single point. 4.The apparatus of claim 3 wherein the terminal assemblies include aconducting stud and a fusible link electrically connected between thestud and associated conductive arc.
 5. The apparatus of claim 1 whereinthe respective sets of conductive arcs are of different radii tofacilitate cooling.
 6. The apparatus of claim 1 wherein the respectivesets of conductive arcs are disposed concentrically, axially displacedfrom each other.
 7. The apparatus of claim 1 further including anon-conducting mounting structure cooperating with the sets of arcs tomaintain the arcs in predetermined disposition.
 8. The apparatus ofclaim 7 wherein the mounting structure maintains the sets of arcsconcentrically and axially to expose the arcs to cooling fluid atambient inlet temperatures
 9. The apparatus of claim 3 wherein thesingle point of connection to the arc is approximately at the midpointof the arc.
 10. The apparatus of claim 1 wherein the arcs are formed ofrod stock.
 11. The apparatus of claim 1 wherein the conductive arcs areformed of rectangular stock and include respective notches adapted toreceive the individual windings.
 12. The apparatus of claim 1 whereinthe collecting conductor arcs are relatively rigid such that theymaintain their shape during accelerations encountered during normaloperation.
 13. The apparatus of claim 1 wherein individual phase coilscorresponding to each magnetic pole in the rotor are evenly distributedbetween sets of conducting arcs.
 14. The apparatus of claim 1 whereinthe collecting conductors each comprise, for each electrical phase, aset of two electrically isolated, equally sized conductive arcs.
 15. Theapparatus of claim 1 wherein the collecting conductors each comprise,for each electrical phase, a set of four electrically isolated, equallysized conductive arcs.